Brandi Glanville at the release party for her new book "Drinking & Tweeting"Splash News

Brandi Glanville has revealed the very awkward moment she knew her husband Eddie Cibrian was cheating with LeAnn Rimes.

She writes in her tell-all memoir “Drinking & Tweeting and other Brandi Blunders,” (via RadarOnline) that she went on a double date that ended with Cibrian and Rimes singing “I Got You Babe.”

In 2009 she had traveled to Calgary where Cibrian was filming a Lifetime movie called “Northern Lights” where the country star was also his co-star.

Glanville allegedly insisted upon meeting the “Blue” singer, so Cibrian set up a double date at a sushi restaurant with his co-star and her then-husband, Dean Sheremet.

She writes, “And this woman, whom I had just met, spent more time flirting with my husband than acknowledging her own. And Dean, bless his heart, ate his sushi, laughed at all the right moments, and pretended that he didn’t see exactly what was in front of him.

“As the evening progressed, every time LeAnn made some sort of inappropriate advance toward my husband – a whisper, a giggle, or a reach across the ever-shrinking table – Eddie squeezed my hand a little tighter. And as if on cue, Eddie would lean over the table, every so often, to offer me a nervous, overly tongue-y kiss to gauge my current state of mind.”

Later that night, as Cibrian and Rimes performed their karaoke number together, the “Real Housewife” realized her husband was sleeping with the singer.

She writes: “When later that same night, LeAnn awkwardly pulled my husband (not hers!) onstage for an awful karaoke rendition of Sonny and Cher’s “I Got You Babe,” I just about lost it… Was she serious? I felt like I was in the twilight zone.”

She continues, “Being the devoted housewife and trusting partner, I wasn’t going to say anything to them, but I knew that kind of tenacity didn’t come from nowhere. I looked at Eddie’s smiling face on that stupid, low-rent stage and leaned over to Dean and said, ‘You know they’re f–king, right?’”

She says Sheremet didn’t respond, and they both chose to ignore their “gut feeling” of infidelity until both of their marriages ended.

Soon came the “final f–king straw” (her words) when she realized they were more than just friends.

She writes, “LeAnn had ‘accidentally’ smeared some cake frosting on her top ( she was still a bigger girl and completely flat-chested at the time) and asked my husband, not realizing that I was standing behind the both of them, if he’d wanted to lick it off her. This woman asked my husband if he wanted to eat the frosting mess she’d dropped on her nonexistent chest? Are you f–king kidding me? He hadn’t realized I was there either, and he laughed with hungry eyes at the suggestion.”

Glanville writes that she stepped in between them and said, “’What the f–k do you two have going on? Do you two have something you’d like to tell me?’ LeAnn laughed through her oversized dentures before purring. ‘Oh, honey, you’re just being silly.’” Glanville immediately stormed out of the restaurant.

She recalls that Cibrian tried to brush off the encounter. “He convinced me I was just being paranoid,” she writes. “I even asked him about the frosting incident, and he told me, ‘You see and hear things that don’t actually happen.’ I wanted to believe him so desperately that I let him convince me that I just made it up in my head.”